This invention relates to electrical connectors. More particularly, it relates to insulation piercing contacts useful in electrical plugs, especially for the telephone industry.
In recent years, the telephone industry has begun to use modular plugs and jacks to make connections between such things as a telephone drop cord and a hand set. The plug normally includes a monolithic plastic housing having a number of groove-like openings in its front end and top side for receiving a like number of contacts which are terminated to insulated conductors. The top surfaces of these contacts are adapted to make electrical connections with the contacts of an associated jack. A cable having a plurality of insulated conductors is received in the back end of the housing.
An example of such a plug which has become somewhat of a standard in the industry is described in U.S. Pat. No. 3,860,316 in the name of Hardesty. The Hardesty patent shows an insulation piercing contact received in the plastic housing. Each contact includes a pair of arrowhead-shaped pointed barbs which pierce the insulation about the conductor as well as the conductor itself. Furthermore, these pointed barbs may actually pierce into the bottom side of the plastic housing. One of the problems of the industry in utilizing this type of contact in this housing is that manufacturers have not been able to use inexpensive solid and stranded copper conductors in cable which is thusly been terminated.
The standard conductor material for this type of telephone cord is tinsel, a very soft material, and thus easily penetrated by the barbs of the contact. One of the problems of using tinsel conductor in lieu of ordinary stranded or solid copper conductor is that it is very expensive. Also, since the tinsel is a soft material, it is easily broken. Thus, it is desirable to utilize a termination system which may be used with ordinary solid or stranded copper conductor.
Another problem in using a contact such as that shown in the Hardesty patent is that the contact can readily work its way free from the conductor because of this arrowhead pointed shape of the insulation piercing members.